Mechanism for laterally aligning sheets

ABSTRACT

The invention relates to a mechanism for laterally aligning sheets, said mechanism comprising a suction device that grips the sheets and guides them with the side edges against a side lay. The mechanism comprises at least one suction plate provided with suction holes. The invention modifies a mechanism for laterally aligning sheets in such a way that heavy and special print substrates can be gripped and aligned easily by the side edges. The mechanism of the present invention comprises suction openings ( 8.1 ) of the suction holes ( 8 ) open into grooves ( 9 ), which are open towards the sheets to be aligned (FIG.  1 ).

FIELD OF THE INVENTION

The invention relates to a mechanism for laterally aligning sheets, saidmechanism comprising a suction device, which grips the sheets and guidesthem with the side edges thereof against a side lay and which comprisesat least one suction plate provided with suction holes.

BACKGROUND OF THE INVENTION

Mechanisms for laterally aligning the sheets that are usually fed in acontinuous stream operation to a printing machine are generally known,and are arranged in the feed table in such a way that the suction deviceis flush with the surface of the feed table. The suction devicecomprises at least one suction plate provided with suction holes,wherein the suction holes open into the surface of the suction plate.The suction holes are supplied cyclically with suction air, to whichevery sheet located over the suction device is sucked, the suctiondevice being displaced transversely to the sheet conveying direction bya drive so that the sheet is guided with its side edge against a sidelay and thus aligned by its side edge.

When processing heavy or special print substrates, such as unilaterallycovered corrugated cardboard carton, it is necessary for the suctiondevice to realize a high retention force. This is achieved in DE 44 15494 C2 by providing a sucker next to the suction plate, said suckerbeing provided on its side facing the sheet with depressions andgrooves, which are provided with suction air via a central hole. Inaddition, an annular gap is provided between the outer periphery of thesucker and the suction device, said annular gap also being supplied withlow pressure for increasing the retention force in the case of heavyprint substrates. In spite of this measure, it is not possible for thesuction device to grip the entire pallet of the heavy or special printsubstrates arriving for processing and to align them reliably inrelation to the side edge. It is therefore necessary to provide a pushlay for this purpose and to mount it if required. This leads toadditional expenses and also a format limitation.

SUMMARY OF THE INVENTION

It is the object of the invention to modify a mechanism for laterallyaligning sheets in such a way that heavy and special print substratescan be gripped and aligned easily by the side edges.

Said object is attained according to the invention by a mechanism inaccordance with the characteristics specified in Claim 1.

The solution according to the invention permits even heavy printsubstrates or print substrates, which due to their design cannot begripped reliably by the suction device guiding the sheet against theside lay, to be aligned easily by the side edges. In doing so, themechanism is realized without any format limitation.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention are represented in thedrawings and will be described in greater detail in what follows.

FIG. 1, is a schematic representation of a suction device,

FIG. 2, illustrates a section along the line A-A shown in FIG. 1,

FIG. 3, illustrates a section along the line B-B shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a suction device (1) that comprises a suction plate(2) and e.g., a double sucker (3). The suction device (1) is arranged ona suction pulling rail (4) that is moved transversely in a sheetconveying direction (5) in the machine cycle, towards a fixedly arrangedside lay (6) and which is guided back by the latter. For this purpose,the suction pulling rail (4) is mounted displaceably in a feed table (7)with the surface of the feed table (7) flushed with the surface of thesuction pulling rail (4). In the suction plate (2), suction holes (8)are provided, which are supplied with low pressure using a suction box(not illustrated) connected to a vacuum system. The suction holes (8)are provided with suction openings (8.1), which open into the base (9.1)of grooves (9). The grooves (9) are arranged in the suction pulling rail(4) or in the suction plate (2) and are open towards the sheet to bealigned. The grooves (9) can be arranged in any position on the suctionplate (2). That is, as illustrated in FIG. 1, they can be arranged inthe suction plate (2) transversely to the sheet conveying direction (5),or parallel or at an inclination thereto. If the grooves (9) arearranged transversely to the sheet conveying direction (5) or at aslight inclination thereto, it is advantageous to prevent the conveyedsheets from getting stuck by designing the groove walls (10) located atthe front in the sheet conveying direction (5) in such a way that theyare inclined towards the sheet conveying direction (5). An angle, α, ofapproximately 60° has proved to be advantageous for this purpose.

The sheets are conveyed in a continuous stream operation from a belttable towards the feed table (7) in the known manner and the respectiveforemost sheet of the stream of sheets is transported with its leadingedge against front lays positioned on the feed table (7) and thusaligned by its leading edge. Thereafter, if double suckers (3) arearranged in the suction pulling rail (4) as in the exemplary embodiment,said double suckers (3) and the suction holes (8) of the suction plate(2) are activated by supplying them with low pressure. By arranging thesuction openings (8.1) in the base (9.1) of the grooves (9) open towardsthe sheet to be aligned, instead of arranging them on the surface of thesuction plate (2), the effective suction surface of the suction plate(2) is increased. Furthermore, it has been observed that the corrugationin unilaterally covered corrugated cardboard cartons, or the material inheavy print substrates is not merely pulled against the suction plate(2) after low pressure is supplied to the grooves (9). Instead, itundergoes slight deformation elastically so as to fit the contour of thegrooves (9). A more or less form fit between the sheet to be aligned andalso the grooves (9) of the suction plate (2) is thus realized and ahigh pulling force is made possible. As a result, heavy or special printsubstrates are gripped reliably and likewise guided with the side edgeagainst the side lay (6).

Subsequently, the suction air supply to the double sucker (3) and alsoto the suction plate (2) is interrupted in the known manner and thesheet aligned by the leading edge and side edge thereof is conveyed intothe machine arranged downstream.

Since the suction pulling rail (4) with grooves (9) that are opentowards the sheet to be aligned is not suitable for aligning arbitraryprint substrates, said suction pulling rail can be replaced. For thispurpose, holes (11) are provided in the suction pulling rail (4) so asto be able to connect the suction pulling rail (4) to a slide, which canbe mounted in the feed table (7) and displaced transversely to the sheetconveying direction (5) in the work cycle. It is also possible to designonly the suction plate (2) to be replaceable and to replace it wheneverrequired.

LIST OF REFERENCE NUMERALS USED

-   1 Suction device-   2 Suction plate-   3 Double sucker-   4 Suction pulling rail-   5 Sheet conveying direction-   6 Side lay-   7 Feed table-   8 Suction hole-   8.1 Suction opening-   9 Groove-   9.1 Groove base-   10 Groove wall-   11 Hole-   α Angle

1. A mechanism for laterally aligning sheets, said mechanism comprisinga suction device, which grips the sheets of paper and guides them withthe side edges thereof against a side lay and which comprises at leastone suction plate provided with suction holes, said mechanism beingcharacterized in that suction openings (8.1) of the suction holes (8)open out into grooves (9), which are open towards the sheets to bealigned.
 2. The mechanism of claim 1, wherein said suction openings(8.1) are arranged in the base (9.1) of said grooves (9).
 3. Themechanism of claim 1, wherein said grooves (9) are arranged transverselyto said sheet conveying direction (5).
 4. The mechanism of claim 1,wherein said grooves (9) are arranged parallel to said sheet conveyingdirection (5).
 5. The mechanism of claim 1, wherein said grooves (9) arearranged such that they are inclined towards said sheet conveyingdirection (5).
 6. The mechanism of claim 1, wherein said suction plate(2) is accommodated in said suction pulling rail (4).
 7. The mechanismof claim 6, wherein said suction plate (2) is designed to bereplaceable.
 8. The mechanism of claim 6, wherein said suction pullingrail (4) is designed to be replaceable.